Volumetric meters are commonly used in agricultural seeding implements such as grain drills and air seeders to meter the seed. Volumetric meters are also used with fertilizer or other chemical applicators. A volumetric meter often employs a meter roller contained within a housing that defines an inlet for receiving product from a tank and an outlet for dispensing metered product. The meter roller is fluted so that as the roller is rotated, product from the tank is carried to the outlet in a controlled manner based on the size of the roller flutes and speed of rotation of the roller. From the meter housing, the seed is carried by a distribution system for dispensing to the soil. The distribution system typically includes a number of individual channels each receiving seed from a defined section of the meter roller. The distribution system may be a gravity system that guides the seed as it falls by gravity from the meter to the soil. Alternatively, the distribution system may be pneumatic, using flowing air to distribute the seed from the meter. A pneumatic distribution system typically has a plurality of primary distribution lines, each supplied with product from a defined section of the meter roller. Typically, product flowing through each primary distribution line is later divided into several secondary distribution lines, each directed to an individual crop row in the soil.
In contrast to a volumetric seed meter, row crop planters use individual seed meters located at each row unit. These meters are supplied by either individual seed hoppers mounted to the row unit or supplied with seed from a central tank, often with a pneumatic system to deliver the seed. The seed meters, however, instead of metering the seed based on volume, singulate the seed and deliver one or more seeds upon specified intervals. Recent products have been made available on row crop planters that shut-off the flow of seed at the individual row units. This is often accomplished by a clutch mechanism in the seed meter drive that is actuated to disengage the seed meter drive. These have met with commercial success as customers seek to control costs by eliminating any double seeding such as can occur at the edge of a field when the area remaining to be seeded is not as wide as the planter or in a non-rectangular field where the rows do not all end at the same location. Since the seed shut-off is at the individual meter mounted on the row, there is only a short delay or no delay from the time the meter is shut-off until the flow of seed at the soil is stopped.
To provide a similar shut-off on a volumetric meter having an air, i.e. pneumatic, distribution system, a number of unique challenges must be overcome that do not exist with a row crop planter. These challenges include: 1) if seed is stopped from flowing into the meter, there is a long delay until seed stops flowing at the discharge since the meter housing must empty before seed flow stops; 2) air seeders may mix multiple products within the airstream so that stopping the flow of seed to the ground by redirecting the air flow after the seed is introduced into the airstream requires separation of the mixed products; and 3) with some air seeders, the product tanks are pressurized during operation, further complicating the return of redirected product to the tank.
One approach to providing a sectional meter shut-off is shown in US patent application publication number 2009/0079624, published Mar. 26, 2009. Slidable gates are positioned between the product storage tank and the meter roller. Individual actuators are provided to move each gate between open and closed positions. Because the gates are positioned between the storage tank and the meter, after actuation of the shut-off actuators, product will continue to flow until the meter is emptied of product. Thus this arrangement does nothing to address the first challenge listed above.